This invention relates generally to seal structures and, more particularly, to a condensate seal around the shaft of a draft inducer motor for a condensing furnace.
An induced draft furnace is one in which the combustion process is supported not only by the natural convection of air through the unit but also by a motor driven, or induced draft, blower to accelerate the flow of air to the combustion chamber. The induced draft blower can be either a blow-through or a draw-through type, but is most commonly used downstream of the heat exchanger(s) to draw the combustion gases from the heat exchanger(s) and out the flue. The induced draft blower is particularly needed where there is a significant pressure drop across the heat exchanger(s), such as in the case of a condensing furnace wherein, in addition to the primary heat exchanger, there is a condensing heat exchanger which extracts from the combustion gases not only additional sensible heat but also the latent heat which causes a phase change from the gaseous to a liquid state. The resulting condensate is normally drained from the condensing heat exchanger by an appropriate drainage tube. However, there is a certain amount of condensate that is drawn up into the inducer blower wheel as the combustion gases are discharged into the flue. This condensate then tends to migrate from the blower wheel, along the motor shaft, into the inducer motor where it can enter the bearings and cause damage thereto because of the relatively high acid content in the condensate.
One method of preventing the migration of condensate along the motor shaft is to provide a seal around the motor shaft where it penetrates the wall of the inducer housing. However, this approach may be in conflict with the need to provide relative movement of the inducer motor with respect to the inducer housing. That is, in order to reduce the motor vibration during operation of the system, the motor may be mounted on elastomeric grommets that relax and settle over time. Thus, both the motor and the shaft will move within the penetration opening of the inducer housing. A normal seal device will therefore not satisfactorily perform in this environment.
It is therefore an object of the present invention to provide an improved seal device for the shaft of an inducer motor.
Another object of the present invention is the provision in an induced draft blower for preventing the migration of condensate to the electric motor.
Yet another object of the present invention is the provision in an induced draft blower for reducing inducer motor vibration.
Still another object of the present invention is the provision in an induced draft blower for a condensate seal that is economical to manufacture and effective in use.
These objects and other features and advantages become more readily apparent upon reference to the following description when taken in conjunction with the appended drawings.